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Positional Astronomy at Melbourne Observatory
Image: Album - Photographs
Source: Museum Victoria
Along with the observations required for timekeeping, positional astronomy occupied the largest part of the Observatory's work. Positional astronomy consisted of the accurate and repeated observations of stars, and then the reduction of the observations to provide a precise location of the star in the sky and its magnitude. When the Melbourne Observatory commenced, this involved the use of the transit telescope and accompanying equipment to fix the location. By the 1880s celestial photography had improved so that it was possible to take series of photos of the sky, then measure the position and magnitude of stars on the photographic plates.
The work of the Melbourne Observatory was of particular importance because it was one of the best equipped observatories in the southern hemisphere, and thus able to observe stars that could not be seen from the European and North American observatories.
In the early years Melbourne Observatory became involved in several international projects. In 1863 Government Astronomer Robert Ellery took observations of the parallax of Mars in conjunction with Greenwich Observatory near London and Pulkowa Observatory in St Petersburg; this was to provide measurements that would aid the calculation of the distance of the Earth from the Sun. The following year, in collaboration with Greenwich Observatory, the Observatory was making observations of the polar distances of stars, to measure the amount of apparent displacement due to the refraction of the Earth's atmosphere. Prior to the Transit of Venus in 1874, the Observatory made large numbers of transit observations of stars that would be used by expeditions from the northern hemisphere observatories to locate the precise position of their field observatories.
Several projects were aimed at measuring as accurately as possible the distances between the planets and the Sun, and therefore understanding the mechanics of the solar system. For example, in 1931 the Observatory used its astrographic telescope to photograph the passage of the minor planet Eros; the photographic plates were sent to Greenwich where astronomer Spencer Jones used them with those from other observatories to more accurately measure solar parallax. His work would not be improved upon until the advent of radio astronomy after the Second World War permitted radar measurements of the distance between Earth and Venus.
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Astronomical regulator clock designed by Government Astronomer Robert Ellery and built at Melbourne Observatory in 1888. The clock was probably made by Observatory instrument maker Carl ...From: South Yarra, Australia Images: 16
Standard maximum Fahrenheit thermometer, by R. & J. Beck, London. Range -10 to +120 degrees. Used at Melbourne Observatory.From: London, United Kingdom Images: 1
Solar radiation thermometer, made by Grimoldi, Melbourne. Range -10 to +200 degrees Fahrenheit. For measuring maximum temperature attained in full rays of sun. Used at Melbourne Observa ...
Sterneck pendulum gravity apparatus for measuring value of g, the acceleration due to gravity. In 1893, Pietro Baracchi made observations at Melbourne Observatory for comparison with ...From: South Yarra, Australia Images: 2
Altitude and azimuth instrument, or altazimuth, 18 inch circle, made by Troughton & Simms, London, circa 1836. This instrument was used for the Geodetic Survey of Victoria, 1858-71, whi ...From: London, United Kingdom Images: 8
"Star Turn" surface hardness comparator in bakelite case. Used to measure the hardness of materials as measured in the Rockwell C scale. The measurement is made by rubbing pins across ...From: London, United Kingdom Images: 3
Thomson astatic differential galvanometer, by Elliott Bros, London. Used at Melbourne Observatory. A galvanometer measures electric currents.From: London, United Kingdom Images: 1
Dial pattern rain gauge, made by Thomas Gaunt, Melbourne & London. Zinc funnel with square brass rim. Used at Melbourne Observatory. Used to measure the amount of rainfall.
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Fahrenheit thermometer, made by T. Gaunt & Co., London & Melbourne. Range 0 to 120 degrees. Used at Melbourne Observatory.From: Melbourne, Australia Images: 0
Recording thermometer in a glass case, made by T. Gaunt & Co, Melbourne. Graph indicates temperature changes over one week. Used at Melbourne Observatory.